1. Field of the Invention
The present invention relates to a ball grid array zero insertion force socket for a CPU package, especially a socket having two pieces of bases, one for mounting solder balls thereon, and the other for receiving a cam lever to move a cover which is movably mounted on the bases.
2. The Related Art
Ball grid array zero insertion force (ZIF) sockets are usually installed with a cam lever for controlling insertion/withdrawal of a CPU package. For achieving low profile requirement, the cam lever is normally operated in a horizontal manner. Therefore, the cam lever is particularly received in a lever reception area which is adjacent to and not overlapped with a contact reception area to a bottom of which solder balls are mounted. However, solder balls mounted on the bottom of the contact reception area can not be soldered on a printed circuit board coplanarly due to the weight of the lever reception area. For example, FIG. 4 illustrates a socket 1 having a cover 11 moveably engaged with a base 12 and a cam lever 3 pivotably received between the cover 11 and the base 12 and operative to move the cover 11 in opposite directions for respectively rendering the socket into a loosened status for receiving CPU pins with substantially zero insertion force or into a tightened status for engaging the inserted CPU pins with contacts retained in the base 12. The details of this socket may be referred to U.S. patent application Ser. No. 09/128,769, which is assigned to the same assignee of the present application and enclosed herein for reference. The socket 1 has a plurality of solder balls 8 mounted to a bottom of a contact reception area 1A which is adjacent to a lever reception area 1B. The socket is electrically connected to a printed circuit board 9 via a reflow soldering procedure on the solder balls 8. Since another half bottom portion of the socket 1 has no solder balls mounted thereto, some of the solder balls are apt to be cold soldered to the printed circuit board due to the unbalanced weight of the lever reception area.
It is requisite to provide a new ZIF socket which can solve the soldering problem as encountered in FIG. 4.